The heavy bellows cloth which is used to cover things like pumps and
reservoirs has been the source of most of my worries, generally.  Some
years ago, I stripped some original Duo-Art cloth with acid and dis-
covered that the rubber inside, when it has not been torn out of the
material, measured about 35 thousandths thick.

I sent a large sample of this to Player Piano Co., who in turn sent it to
their cloth company, but for some reason, it was never made.  Durrell
asked, "How do I specify this cloth to them?"  I suggested that he have
them analyze it and tell him what he had.  At the same time, I suggested
that he also ask them to give him a test he could make to assure the
company that he had what he ordered, _before_ he gave them the order.
I wasn't in on the buying of this stuff.

Coatings thicker than about .015 inch have to be made differently, in a
process called "calendaring," or something like that.  It is a much more
expensive process, and would probably have priced the cloth out of this
solar system.  However, I have always added cabretta leather punchings to
all the folding corners of the cloth and haven't had any more problems
with the thinner rubber on rotary pumps.

Without the cabretta, however, a player pump wears its cloth out in about
6 months of steady playing.  We're talking _holes_ here -- those you can
stick a pencil through.  But if the leather is put over those folds when
new, (and I just use hot hide glue) after the cloth has been clamped
tightly to crease it first, the cloth holds up for at least 18 years and
counting.

What causes most pump problems today anyway is the old, unrestored inside
flap valves and seats.  In 99% of the cases, these were never rebuilt,
and so the pump must be completely torn down again.  You will notice that
inside flap seats usually just zip off with light pressure from a putty
knife.  They will have completely dry-rotted away.  It seems to be an
accelerated process.  What may have been tough and tight ten years ago is
now rotting away to dust.

Craig Brougher